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Full text of "The Cambridge Natural History"

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has  remained.     This  fact,   therefore,   shows   that   the   mammal
cannot  have been   derived  from a  hird-like  ancestor,  but   that

FIG. 43.—JLepus cuniculus.    Ven-
tral view of the vascular sys-
tem.    The heart is somewhat
displaced  towards  the left  of
the   subject;   the   arteries   of
the right and the veins of the
left side are in great measure
removed.   a.epgt internal mam-
mary artery; a./1, anterior facial
vein ; a.m,, anterior mesenteric
artery ;, anterior phrenic
vein ;    az~v,   azygos vein ;   brt
brachial artery ;, common
iliac   artery ;,   common
iliac vein ; cce, coeliac artery ;, dorsal aorta : e.c, external
carotid artery ;<a, external
iliac   artery j   e.iLv^    external
iliac vein ; e.ju, external jugu-
lar vein ; fm,*at femora] artery ;
fm.v, femoral vein ; h.v, hepatic
veins ;     i.c,   internal     cai-otid
artery ; i,cs, intercostal vessels;
iM.a, internal iliac artery ; -i.iLvt
internal iliac vein ; iju, internal
jugular   vein ;    i.l,   iliolumbar
artery and vein ;   in, innomin-
ate artery ;, left auricle;
l.c.c, left  common carotid ar-
tery ;, left pre-caval vein;
l.v, left ventricle ;, median
sacral artery ;  p-a, pulmonary
artery; p. epgr, epigastric artery
and vein ; jp.f,  posterior facial
vein, j,   posterior   mesen-
teric   artery;  p*pht  posterior
phrenic veins ; jpt.c, post-caval
vein ; j>.-», pulmonary vein ; r,
renal  artery  and  vein ;   r.ait,
right auricle • r.c.c, right com-
mon carotid artery ; r.prc, right
pre-caval vein ; r.v, right ven-
tricle ;   s.d.a, right subclavian
artery ;  s.cZ.-u, subclavian vein ;
&pm,>   spermatic   artery ;    s.vs,
vesical artery; tit, uterine artery
and vein ; vr, vertebral artery.
(From Parker's

both must have independently come from an ancestor with
both halves of the aortic arch present, of which one half
has disappeared in one group, and the other half in the
other. It is an interesting fact, too, to notice that the four